RockBox album cover appearing white'ish

[ISwearSheWas18]

Hello, I recently started using Rockbox, when I noticed, that for some image files, which I have set as album artworks for some songs, appear slightly white'ish or much more grayer than the original image. Like the brightness of that image is messed up or something. Most of the images are ok, just like 10-20% have this defect. Any ideas what could cause this thing?

[electric_indigo]

I also came across this issue. At first I thought there was some bug in display driver, but I took a screendump of a distorted image and it turned out pale on my PC, too. Then I thought the vulnerable images had been encoded by buggy software or with some exotic settings, so I re-encoded them with imagemagick (with the -strip option) and it didn't help. But the funniest thing is that I even took a screenshot of a certain image on my PC (where it looked properly) to eliminate previous encoders' influence. After saving the screenshot and copying it to my player, it was still pale / too bright. It seems as if some colors were not handled properly by Rockbox's image libraries.
I run 3.13 on Sansa Clip Zip.

[[Saint]]

It /could/ be a problem with scaling perhaps?

You could test this by making sure the image doesn't need to be resized. You can open the .wps and find the size the theme is expecting, there's be a line along the lines of: %Cl(xpos,ypos,width,height).


[Saint]

[electric_indigo]

I don't know, will try later. However, the images are also affected when viewed in Rockbox's image browser, in any scale.

[ISwearSheWas18]

Just tried, what [Saint] suggested - re-sized images to 96x96 resolution, which is Clip Zip's native one. Surprisingly, for one cover it worked and it appeared as it should. But when I tried to that to some others, they still had the same color defect as before.

[dreamlayers]

My first thoughts were gamma errors in scaling or colour profile issues. Those seem to have been ruled out by resizing and taking a screenshot on a PC.

Please upload some problem images somewhere so developers can examine the issue.

As a workaround, try converting the album art to BMP format. I suggest resizing them first to make the files smaller.

[ISwearSheWas18]

Hmm, tried to convert images to .bmp as suggested and now it looks as it should. No need to re-size images to 96x96, just converting them to .bmp does the trick. Thanks for help!

[[Saint]]

Just tried, what [Saint] suggested - re-sized images to 96x96 resolution, which is Clip Zip's native one.

Perhaps I could've worded this better. This wasn't quite what I was suggesting, but, close.

The native resolution of the device isn't relevant unless the theme is actually using a full screen album art image, which I doubt somewhat.
What I was suggesting was to look at the .wps/.sbs itself (as noted in my previous post you'll be looking for a declaration along the lines of:
%Cl(xpos,ypos,width,height,alignment,alignment) - the alignment params are not required and may or may not be present) and see what size album art the theme is requesting. By supplying the exact proportions the theme expects we can avoid any {down|up}scaling being done on the image at all.


[Saint]

[electric_indigo]

Some examples: http://imgur.com/a/5NPCm
Some of them have not only color distorted, but also have some kind of “offset”.
Resizing to player's native resolution fixed the problem for all the images. Converting to bmp and back to jpeg without resizing fixed it for most of them. I used imagemagick with default quality settings.

[ISwearSheWas18]

Well, it was quite the opposite for me. Converting image files to .bmp and leaving them to that format without converting back to .jpeg fixed all images, while changing resolution affected only few of them.

[dreamlayers]

Some examples: http://imgur.com/a/5NPCm
Some of them have not only color distorted, but also have some kind of “offset”.
Resizing to player's native resolution fixed the problem for all the images. Converting to bmp and back to jpeg without resizing fixed it for most of them. I used imagemagick with default quality settings.

I'm seeing the problems you describe in the image viewer plugin, on the 5G iPod and 5G simulator, d561017. This seems like a JPEG decoder issue.

These weren't fixed by converting to bmp and back: http://i.imgur.com/rmdguNT.jpg http://i.imgur.com/iTHqXDL.jpg
Note that they're both overall dark images, with large fairly uniform areas. The new JPEGs both seem to show some corruption near the top in Rockbox, like the first few rows of blocks aren't decoded properly, and proper decoding starts after a certain point.

[Roboturner913]

I've had this issue in the past on encoded on covers with a lot of dark/black colors. It's always the same few covers that do it too.

I think for some reason Rockbox can't handle all of the darkest color info, especially when there are gradients of black. I lightened the cover a bit through Photoscape and that seemed to work. The good news is that once you fix it and re-tag the files it's done for good and you shouldn't have to mess with it again.

Probably the reason bitmapping works sometimes is because you're throwing out a lot of the subtler color info (i.e. instead of 10 shades of black there are now only 2 or 3) so it's not nearly so difficult for the program to read and process.

[Nephiel]

I'm also having this issue.

The file I was trying to use as a backdrop for the menus is a very dark figure fading onto a black background. It's a BMP file I resized to 96x96 (the native resolution of the Zip) so no resizing is done by Rockbox. However the figure appears very bright on the screen of the Clip Zip, the edges are very clearly defined, with a high difference in brightness between "pitch black" and "very-nearly-black gray".

Yet on a computer the screen dumps look the same as the original image (black and dark gray look nearly the same brightness), so the bug must be in the OLED screen or its driver...

[Nephiel]

Here's a file which appears to be fine on a computer yet shows artifacts when viewed on a Clip Zip. My bad, that image had artifacts indeed.

[ZincAlloy]

Some mp3s I got from amazon have embedded album art that will produce blue artifacts.